Thank you for the reply! I have checked your idea.
It seems the options /MANIFEST:EMBED /MANIFESTINPUT:<my.manifest> are not compiler options, but /MANIFEST:EMBED is a linker option.
I saw no use for MANIFESTINPUT:<my.manifest>.
The idea to use /MANIFEST:EMBED as a linker option is a good one, but it does not address the problem reported regarding C::B post build steps:
As you can see from the image attachment of my first post, I did run 2 post build steps. The first was MT.exe, the second is a utility 'cpde_usr' I have written to export header files etc. to an external folder structure. After eliminating MT.exe as a post build step, I am now experiencing that my own utilty cpde_usr is failing for the exact same reason: The post build step is being executed before the build target is ready (i.e. build target file is not closed).
I still think this is a C::B problem related to post build steps in general. If I run 'cpde_usr' manually after, it works fine with the same input.